Here is what I do using Vuescan and LR which results in the original TIFF files being untouched:
1) Scan to a directory ("scans") using Vuescan. I set Vuescan to automatically create the file names. My file naming is simply the roll and frame number resulting in a name like Roll-50-Frame-04.dng. The files are TIFF in dng format I also allow Vuescan to neg-pos inversion. I scan these to TIFF/DNG and also save a JPG simply as a kind of thumbnail. I never touch the JPG as it is a lossy format.
2) Import the TIFF file and convert to DNG in LR. The files get converted and copied to a different destination on import. I make a virtual folder (i don't remember exactly what this is called in LR) for the images by roll number.
3) Alter them in LR to my hearts content. These are the copies that LR made when the files were imported.
4) Move the TIFF files originally scanned from the "scans" directory to another directory ("/scans/camera/roll 50")
5) All of my negatives go into PrintFile pages and are labeled by roll number.
6) Each negative pages goes in a 3-ring notebook. I print a negative information page that goes with the negative page that contains information about the film, camera, date, exposure info, development info, and other notes as needed.
OK, I know that is more than with the OP asked for, but my system allows me to go back and forth between the negative, original TIFF scan, and altered files in LR. The three-ring notebook serves as my ultimate back up as it requires no power. I also periodically back up my original TIFF scan directory to a second computer. I have been meaning to use an off-site storage solution, like Carbonite, but have not done so yet.
Note: As stated in other responses, LR does not alter the original (imported) TIFF/DNG files. I'm not sure how it handles JPG but I believe it does alter the JPG file and does so in a manner that you cannot get the original JPG back. It is possible to come back to an "altered" (imported) TIFF/DNG after some time (weeks/months/years), undo all of the changes to a file, and get back the original TIFF image since LR does not alter the original TIFF image.
Another way to think about how LR "alters" an image is like a recipe. A recipe does not cook the meal for you. A recipe is a set of steps that when followed result in a meal. LR saves the steps that you do when you "alter" an image in LR instead of altering the file itself. It saves these steps as a recipe that gets "cooked" every time you open an image in LR that you have altered.
Import your TIFF's into LR and "edit" them knowing that the original TIFF is not really altered.